Medical device balloon

ABSTRACT

A balloon catheter having a balloon formed at least in part of a blend of a first polymeric material having a first Shore durometer hardness, and at least a second polymeric material having a second Shore durometer hardness less than the Shore durometer hardness of the first polymeric material. The balloon of the invention has enhanced softness and flexibility due to the presence of the second polymeric material, and a lower than expected compliance. In a presently preferred embodiment, the balloon is formed of a blend of polymeric materials comprising polyether block amides.

BACKGROUND OF THE INVENTION

[0001] The invention relates to the field of intravascular catheters,and more particularly to a balloon catheter.

[0002] In percutaneous transluminal coronary angioplasty (PTCA)procedures, a guiding catheter is advanced until the distal tip of theguiding catheter is seated in the ostium of a desired coronary artery. Aguidewire, positioned within an inner lumen of an dilatation catheter,is first advanced out of the distal end of the guiding catheter into thepatient's coronary artery until the distal end of the guidewire crossesa lesion to be dilated. Then the dilatation catheter having aninflatable balloon on the distal portion thereof is advanced into thepatient's coronary anatomy, over the previously introduced guidewire,until the balloon of the dilatation catheter is properly positionedacross the lesion. Once properly positioned, the dilatation balloon isinflated with liquid one or more times to a predetermined size atrelatively high pressures (e.g. greater than 8 atmospheres) so that thestenosis is compressed against the arterial wall and the wall expandedto open up the passageway. Generally, the inflated diameter of theballoon is approximately the same diameter as the native diameter of thebody lumen being dilated so as to complete the dilatation but notoverexpand the artery wall. Substantial, uncontrolled expansion of theballoon against the vessel wall can cause trauma to the vessel wall.After the balloon is finally deflated, blood flow resumes through thedilated artery and the dilatation catheter can be removed therefrom.

[0003] In such angioplasty procedures, there may be restenosis of theartery, i.e. reformation of the arterial blockage, which necessitateseither another angioplasty procedure, or some other method of repairingor strengthening the dilated area. To reduce the restenosis rate and tostrengthen the dilated area, physicians frequently implant anintravascular prosthesis, generally called a stent, inside the artery atthe site of the lesion. Stents may also be used to repair vessels havingan intimal flap or dissection or to generally strengthen a weakenedsection of a vessel. Stents are usually delivered to a desired locationwithin a coronary artery in a contracted condition on a balloon of acatheter which is similar in many respects to a balloon angioplastycatheter, and expanded to a larger diameter by expansion of the balloon.The balloon is deflated to remove the catheter and the stent left inplace within the artery at the site of the dilated lesion.

[0004] In the design of catheter balloons, balloon characteristics suchas strength, flexibility and compliance must be tailored to provideoptimal performance for a particular application. Angioplasty balloonspreferably have high strength for inflation at relatively high pressure,and high flexibility and softness for improved ability to track thetortuous anatomy and cross lesions. The balloon compliance is chosen sothat the balloon will have a desired amount of expansion duringinflation. Compliant balloons, for example balloons made from materialssuch as polyethylene, exhibit substantial stretching upon theapplication of tensile force. Noncompliant balloons, for exampleballoons made from materials such as PET, exhibit relatively littlestretching during inflation, and therefore provide controlled radialgrowth in response to an increase in inflation pressure within theworking pressure range. However, noncompliant balloons generally haverelatively low flexibility and softness, so that it has been difficultto provide a low compliant balloon with high flexibility and softnessfor enhanced trackability.

[0005] Therefore, what has been needed is a catheter balloon withrelatively low compliance, and with improved ability to track thepatient's vasculature and cross lesions therein. The present inventionsatisfies these and other needs.

SUMMARY OF THE INVENTION

[0006] The invention is directed to a balloon catheter having a balloonformed at least in part of a blend of a first polymeric material havinga first Shore durometer hardness, and at least one additional polymericmaterial of essentially the same composition as the first polymericmaterial but compounded to have a Shore durometer hardness less than theShore durometer hardness of the first polymeric material. The balloon ofthe invention has enhanced softness and flexibility due to the presenceof the second polymeric material, and a lower than expected compliance.In a presently preferred embodiment, the balloon is formed of a blend ofpolymeric materials comprising polyether block amides.

[0007] In accordance with the invention, the balloon formed from a blendof polymeric materials preferably has a compliance which is notsubstantially greater than the compliance of a balloon made from 100% ofthe first polymeric material, e.g. a compliance less than about 20%greater, preferably less than 15% greater, and most preferably less than10% greater than the compliance of a balloon made from 100% of thehigher Shore durometer material. In a preferred embodiment, thecompliance of the blend is not greater than the compliance of a balloonformed of 100% of the higher Shore durometer material. Additionally, thepolymeric material blend which forms the balloon has a flexural moduluswhich is less than the flexural modulus of the first polymeric material.The softness and flexibility of a balloon is a function of the flexuralmodulus of the polymeric material of the balloon, so that a balloonmaterial having a lower Shore durometer hardness, which thus provides asoft and flexible balloon, has a lower flexural modulus. Thus, theballoon of the invention has enhanced softness and flexibility, yet doesnot have the increased compliance which would be expected from theamount of the second polymeric component having a lower Shore durometerhardness than the first polymeric component.

[0008] In one embodiment of the invention, the balloon is semi-compliantor noncompliant. The term “noncompliant”, should be understood to mean aballoon with compliance of not greater than about 0.03millimeters/atmospheres (mm/atm). The term “semi-compliant” should beunderstood to mean a balloon with a compliance not greater than about0.045 (mm/atm). In contrast, compliant balloons typically have acompliance of greater than about 0.045 mm/atm.

[0009] The first polymeric material may range from about 10 to about 90%of the blend, and the second component of the blend may range from about90 to about 10%. The blend preferably has an amount of the secondpolymeric material which is greater than or equal to the amount of thefirst polymeric material. In a presently preferred embodiment, theballoon is formed of a blend of polyether block amide polymericmaterials having different Shore hardness. A suitable polyether blockamide copolymer for use in the polymeric blend of the invention isPEBAX, available from Elf Atochem.

[0010] The balloon of the invention is formed by extruding a tubularproduct formed from the blend of the first polymeric component and atleast a second polymeric component. In a presently preferred embodiment,the balloon is formed by expanding the extruded tubular product in aballoon mold. Axial tension may be applied to the balloon duringexpansion, and the balloon may be cooled under pressure and tensionbetween blowing steps. In one embodiment, the balloon is formed byexpanding the extruded tubular product in a series of successivelylarger balloon molds.

[0011] Various designs for balloon catheters well known in the art maybe used in the catheter system of the invention. For example,conventional over-the-wire balloon catheters for angioplasty or stentdelivery usually include a guidewire receiving lumen extending thelength of the catheter shaft from a guidewire port in the proximal endof the shaft. Rapid exchange balloon catheters for similar proceduresgenerally include a short guidewire lumen extending to the distal end ofthe shaft from a guidewire port located distal to the proximal end ofthe shaft.

[0012] The balloon catheter of the invention has improved performancedue to the flexibility, softness, and controlled expansion of theballoon. The polymeric blend provides the surprising result of a balloonhaving relatively low compliance, for controlled balloon expansion, andhaving relatively high flexibility and softness, for excellent abilityto track the patient's vasculature and cross lesions. These and otheradvantages of the invention will become more apparent from the followingdetailed description of the invention and the accompanying exemplarydrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]FIG. 1 is an elevational view partially in section of a ballooncatheter which embodies features of the invention, showing the balloonin an unexpanded state.

[0014]FIG. 2 is a transverse cross sectional view of the ballooncatheter of FIG. 1 taken along lines 2-2.

[0015]FIG. 3 is a transverse cross sectional view of the ballooncatheter of FIG. 1 taken along lines 3-3.

DETAILED DESCRIPTION OF THE INVENTION

[0016]FIG. 1 illustrates a balloon catheter which embodies features ofthe invention. The catheter 10 of the invention generally comprises anelongated catheter shaft 11 having a proximal section, 12 a distalsection 13, an inflatable balloon 14 formed of a blend of polymericmaterials on the distal section 13 of the catheter shaft 11, and anadapter 17 mounted on the proximal section 12 of shaft 11. In FIG. 1,the catheter 10 is illustrated within a patient's body lumen 18, priorto expansion of the balloon 14.

[0017] In the embodiment illustrated in FIG. 1, the catheter shaft 11has an outer tubular member 19 and an inner tubular member 20 disposedwithin the outer tubular member and defining, with the outer tubularmember, inflation lumen 21. Inflation lumen 21 is in fluid communicationwith the interior chamber 15 of the inflatable balloon 14. The innertubular member 20 has an inner lumen 22 extending therein which isconfigured to slidably receive a guidewire 23 suitable for advancementthrough a patient's coronary arteries. The distal extremity of theinflatable balloon 14 is sealingly secured to the distal extremity ofthe inner tubular member 20 and the proximal extremity of the balloon issealingly secured to the distal extremity of the outer tubular member19.

[0018]FIG. 2, showing a transverse cross section of the catheter shaft11, illustrates the guidewire receiving lumen 22 and inflation lumen 21.The balloon 14 can be inflated by radiopaque fluid introduced at theport in the side arm 24 into inflation lumen 21 contained in thecatheter shaft 11, or by other means, such as from a passageway formedbetween the outside of the catheter shaft and the member forming theballoon, depending on the particular design of the catheter. The detailsand mechanics of balloon inflation vary according to the specific designof the catheter, and are well known in the art.

[0019] Balloon 14 is formed of a blend of polymeric materials, which ina presently preferred embodiment comprises a first polyether block amidepolymeric material having a first Shore durometer hardness, and a secondpolyether block amide polymeric material having a second Shore durometerhardness less than the first Shore durometer hardness. The preferredpolymeric material for forming the polymeric blend for the balloon isPEBAX. In one embodiment, the second polymeric material, or the secondpolyether block amide polymeric material, comprises about 20% to about80%, preferably about 40% to about 75%, and most preferably about 50% toabout 60% by weight of the total weight of the blend of polymericmaterials, and the first polymeric material, or the first polyetherblock amide polymeric material, comprises about 20% to about 80%,preferably about 30% to about 70%, and most preferably about 40% toabout 50% by weight of the total weight of the blend of polymericmaterials. Most preferably, the amount of the second polymeric materialis not less than the amount of the first polymeric material. In apresently preferred embodiment, the first polyether block amidepolymeric material has a Shore durometer hardness of about 70D to about72D, and most preferably about 70D, and the second polyether block amidepolymeric material has a Shore durometer hardness of about 55D to about70D, and most preferably about 63D.

[0020] Balloon 14 of the invention preferably has a compliance which isnot substantially greater than the compliance of a balloon consisting ofthe first polyether block amide polymeric material. Balloon 14 has acompliance of about 0.030 mm/atm to about 0.045 mm/atm, and preferablyabout 0.035, from nominal to the rated burst pressure of the balloon,where the nominal pressure is the pressure required to expand theballoon to its working diameter, and the rated burst pressure,calculated from the average rupture pressure, is the pressure at which95% of the balloons can be pressurized to without rupturing. For aballoon of the invention, having an outer diatemeter of not greater than4.0 mm, the nominal pressure is typically about 6 to about 10 atm, andthe rated burst pressure is about 14 to about 16 atm. Balloon 14 has aflexural modulus which is less than the flexural modulus of a balloonconsisting of the first polyether block amide polymeric material.Balloon 14 has a flexural modulus of about 50,000 to about 100,000 psi,and preferably about 55,000 to about 90,000 psi.

[0021] In a presently preferred embodiment, the balloon of the inventionis formed by blow molding an extruded tubular product formed of a blendof the first and second polyether block amide polymeric materials. Theextruded tubular product is expanded to the final working diameter ofthe balloon in a balloon mold. The balloon may be heat set in the mold.In one embodiment, the balloon is blown in a series of successivelylarger balloon molds. Thus, the extruded tubular product is placed in afirst mold and the outer diameter of the tubular product is expanded atelevated pressure and temperature to a first outer diameter. The balloonis then placed in a second, larger mold, and expanded at elevatedpressure and temperature to a second outer diameter larger than thefirst outer diameter. The number of successively larger molds used toexpand the balloon may vary depending on the balloon material and size.To form a 3.0 mm outer diameter (OD) balloon, the tubular member isexpanded in a first mold to an OD of about 2.0 to about 2.5 mm, and thenexpanded in a second mold to the working diameter of 3.0 mm. Preferably,axial tension is applied to the balloon during expansion, and theballoon is cooled in the mold, under pressure and tension, betweenblowing steps. However, the balloon of the invention is preferablyproduced by conventional techniques for producing catheter inflatablemembers in which the extruded tubular product is expanded in a singlemold to the working diameter.

[0022] The balloon 14 has sufficient strength to withstand the inflationpressures needed to inflate the balloon. Balloon 14 formed from a blendof the invention preferably has a burst pressure which is notsubstantially less than the burst pressure of a balloon made from 100%of the first polymeric material, i.e., a burst pressure not more thanabout 15% to about 20% less than, preferably not more than 5% to about15% less than the burst pressure of a balloon made from 100% of thefirst polymeric material. In a preferred embodiment, the burst pressureof balloon 14 is not less than the burst pressure of a balloon formed of100% of the first polymeric material. The average burst pressure ofballoon 14, having an outer diameter of about 3.0 mm, a length of about20 mm and a dual wall thickness of about 0.036 mm is about 18 atm toabout 26 atm. This compares well with the average burst pressure of 18atm to 26 atm for 3.0 mm balloons blown from 100% of the first polymericmaterial. The tensile strength of an American Standard Testing Method(ASTM) “dog-bone” sample cut from a compression molded sheet of materialis about 8,000 psi to about 9,000 psi. The hoop strength, e.g. theproduct of the burst pressure and the balloon diameter, divided by twotimes the balloon wall thickness, of a 3.0 mm balloon of the inventionis about 22,000 psi to about 32,000 psi.

[0023] The catheter shaft will generally have the dimensions ofconventional dilatation or stent deploying catheters. The length of thecatheter 10 may be about 90 cm to about 150 cm, and is typically about135 cm. The outer tubular member 19 has a length of about 25 cm to about40 cm, an outer diameter (OD) of about 0.039 in to about 0.042 in, andan inner diameter (ID) of about 0.032 in. The inner tubular member 20has a length of about 25 cm to about 40 cm, an OD of about 0.024 in andan ID of about 0.018 in. The inner and outer tubular members may taperin the distal section to a smaller OD or ID.

[0024] The length of the compliant balloon 14 may be about 1 cm to about4 cm, preferably about 0.8 cm to about 4.0 cm, and is typically about2.0 cm. In an expanded state, at nominal pressure of about 8 to about 10atm, the balloon diameter is generally about 0.06 in (1.5 mm) to about0.20 in (5.0 mm), and the wall thickness is about 0.0006 in (0.015 mm)to about 0.001 in (0.025 mm). The burst pressure is typically about 18to 26 atm, and the rated burst pressure is typically about 14 atm.

[0025] In a presently preferred embodiment, the balloon 14 typicallyforms wings, which may be folded into a low profile configuration (notshown) for introduction into and advancement within the patient'svasculature. When inflating the balloon to dilate a stenosis, thecatheter 10 is inserted into a patient's vasculature to the desiredlocation, and inflation fluid is delivered through the inflation lumen21 to the balloon 14 through the inflation port 24. The semi-compliantor noncompliant balloon 14 expands in a controlled fashion with limitedradial expansion, to increase the size of the passageway through thestenosed region. Similarly, the balloon has low axial growth duringinflation, to a rated burst pressure of about 14 atm, of about 5 toabout 10%. The balloon is then deflated to allow the catheter to bewithdrawn. The balloon may be used to deliver a stent (not shown), whichmay be any of a variety of stent materials and forms designed to beimplanted by an expanding member, see for example U.S. Pat. No.5,514,154 (Lau et al.) and U.S. Pat. No. 5,443,500 (Sigwart),incorporated herein in their entireties by reference.

EXAMPLE 1

[0026] Polymeric blends were formed using PEBAX 7033 SA01 and PEBAX 6333SA01. PEBAX 7033 (hereafter “PEBAX 70D”) has a Shore durometer hardnessof about 70D, a flexural modulus of 67,000 psi, and tensile strength of8300 psi. PEBAX 6333 (hereafter PEBAX 63D) has a Shore durometerhardness of about 63D, a flexural modulus of 49,000 psi, and a tensilestrength of 8100 psi. PEBAX 70D was blended with PEBAX 63D, where thePEBAX 70D was 40% by weight of the total blend and the PEBAX 63D was 60%by weight of the total blend. The blend was used to prepare 15 samplesof balloon tubing having a mean ID of about 0.018 inch (0.46 mm) and amean OD of about 0.034 inch (0.86 mm), with a blow up ratio of 6.6. Theballoon tubing may be necked in a die before expanding the balloontubing in a mold to form the balloon. A balloon was formed from theballoon tubing by axially stretching the balloon tubing at elevatedtemperature, and expanding the balloon tubing in a balloon mold whileheating the balloon tubing by traversing the length of the mold with aheated air nozzel (at about 360° F. to about 420° F. temperaturecontroller set temperature) at a rate of about 1 mm/sec to about 25mm/sec, and pressurizing the balloon at about 250 psi to about 450 psito an OD of 3.0 mm (for a blow up ratio of about 6.6). The balloon wasthen heat treated in the mold by traversing the length of the mold witha second heated air nozzel, for about 5 to about 30 seconds (at about220° F. to about 300° F. temperature controller set temperature). Theballoon was cooled in the mold. The balloons have an OD of about 3.0 mm,a length of 20 mm, and a mean single wall thickness of about 0.00065inch (0.017 mm) to about 0.00080 inch (0.02 mm). The mean rupturepressure of the balloons was about 20 atm. Radial (OD) compliancemeasurements made on the blown balloons show a compliance of about 0.036mm/atm from a nominal OD of about 3.0 mm at about 8 atm to an outerdiameter of about 3.25 mm at about 15 atm. Table 1 lists the averageballoon OD for the unruptured balloons, at a given inflation pressure.TABLE 1 Inflation Pressure Average Balloon (psi)/(atm) OD (mm) 30/22.603 45/3 2.759 60/4 2.831 75/5 2.887 90/6 2.933 105/7 2.971 120/83.004 135/9 3.038 150/10 3.070 165/11 3.102 180/12 3.132 195/13 3.166210/14 3.202 225/15 3.235 240/16 3.273 255/17 3.315 270/18 3.350 285/193.397 300/20 3.454

EXAMPLE 2

[0027] PEBAX 70D was blended with PEBAX 63D, where the PEBAX 70D was 40%by weight of the total blend and the PEBAX 63D was 60% by weight of thetotal blend. The blend was used to prepare balloon tubing having an IDof about 0.0195 inch (0.495 mm) and an OD of about 0.0355 inch (0.902mm), which was used to prepare balloons having a single wall thicknessof about 0.00065 (0.017 mm) to about 0.0008 inch (0.02 mm), with a blowup ratio of about 6.0, using a procedure similar to the procedureoutlined in Example 1, except that the same heated air nozzel that wasused to heat the balloon tubing during the expansion of the balloontubing in the mold was used to heat treat the entire length of theballoon within the mold after the balloon tubing is expanded in themold. Similarly, a second balloon was formed from 100% PEBAX 70D.

[0028] Radial (OD) compliance and rupture pressure measurement were madeon blown balloons, as listed below in Table 2. The compliance wasmeasured from 8 atm (nominal OD of 3.0) to 14 atm (OD of about 3.25 mm).The balloons formed from a blend of PEBAX 70D and PEBAX 63D hadcompliance equal to the balloon formed from 100% PEBAX 70D. TABLE 2PEBAX PEBAX 70D 70D/63D 100% 60%/40% COMPLIANCE 0.042 0.042 (mm/atm) n =15 MEAN RUPTURE 294 294 PRESSURE (psi) n = 15

EXAMPLE 3

[0029] A first balloon was formed from a blend of 60 weight % PEBAX 70Dand 40 weight % PEBAX 63D. The blend was used to prepare balloon tubinghaving an ID of about 0.019 inch (0.495 mm) and an OD of about 0.0355inch (0.902 mm), and a balloon was formed from the balloon tubing byaxially stretching and expanding the balloon tubing in a first mold at370 psi and 235° C. (temperature controller set temperature) to an OD of2.0 mm, cooling the balloon in the mold at the elevated pressure,expanding the balloon in a second mold at 370 psi and 237° C.(temperature controller set temperature) to an OD of 3.0 mm and a lengthof 20 mm, and cooling the balloon in the mold at the elevated pressure.Similarly, a second balloon was formed from a blend of 80 weight % PEBAX70D and 20 weight % PEBAX 63D, and a third balloon was formed from 100%PEBAX 63D.

[0030] Radial (OD) compliance and rupture pressure measurement were madeon blown balloons, as listed below in Table 3. The compliance wasmeasured from a nominal pressure required to expand to an OD of about3.0 (typically about 6-8 atm) to the pressure required to expand theballoon to an OD of approximately 3.25 mm (typically about 11-16 atm).The balloons formed from a blend of 60 weight % PEBAX 70D and 40 weight% PEBAX 63D, despite the higher weight % of the higher Shore durometerPEBAX polymeric material, had substantially similar rupture pressure andcompliance compared to the balloons formed from 80 weight % PEBAX 70Dand 20 weight % PEBAX 63D. Specifically, the balloons formed of a 60/40blend had lower rupture pressure and higher compliance than the balloonsformed of a 80/20 blend. TABLE 3 PEBAX PEBAX PEBAX 70D/63D 70D/63D 63D80%/20% 60%/40% 100% COMPLIANCE 0.0304 0.0353 0.049 (mm/atm) MEANRUPTURE 311 294 260 PRESSURE (psi) n = 10 AXIAL GROWTH 1.4 1.56 1.98(mm) DUAL WALL 0.038 0.037 0.042 THICKNESS (mm)

[0031] The compliance data for balloons is given below in Tables 4-6.TABLE 4 PEBAX 70D/63D:80%/20% Inflation Pressure Average Balloon(psi)/(atm) OD (mm) 30/2 2.721 45/3 2.777 60/4 2.834 75/5 2.882 90/62.930 105/7 2.965 120/8 2.997 135/9 3.027 150/10 3.056 165/11 3.085180/12 3.114 195/13 3.147 210/14 3.181 225/15 3.217 240/16 3.256 255/173.299 270/18 3.347 285/19 3.403 300/20 3.475

[0032] TABLE 5 PEBAX 70D/63D:60%/40% Inflation Pressure Average Balloon(psi)/(atm) OD (mm) (n = 10) 30/2 2.722 45/3 2.788 60/4 2.849 75/5 2.90490/6 2.943 105/7 2.982 120/8 3.016 135/9 3.048 150/10 3.082 165/11 3.114180/12 3.150 195/13 3.191 210/14 3.228 225/15 3.273 240/16 3.319 255/173.372 270/18 3.441 285/19 3.525 300/20 3.628

[0033] TABLE 6 PEBAX 70D/63D:100% 63D Inflation Pressure Average Balloon(psi)/(atm) OD (mm) (n = 10) 30/2 2.784 45/3 2.864 60/4 2.931 75/5 2.98290/6 3.024 105/7 3.063 120/8 3.102 135/9 3.143 150/10 3.190 165/11 3.242180/12 3.300 195/13 3.360 210/14 3.415 225/15 3.464 240/16 3.541 255/173.639 270/18 3.766

EXAMPLE 4

[0034] Blends of PEBAX 70D and PEBAX 63D were used to form extrudedtubing having an ID of 0.0328 inch and an OD of 0.0568 inch. Flexuralmodulus measurements were made on the extruded tubing using a threepoint bend test. The average flexural modulus from a sample of 6specimens was 15.7 gram/mm for the PEBAX 70D 100% formulation, and was14.4 gram/mm for the PEBAX 70D/63D 80%/20% formulation, and was 11.5 forthe PEBAX 70D/63D 40%/60% formulation. Thus, increasing the weightpercent of the lower Shore durometer material (i.e., PEBAX 63D) didincrease the flexibility of the extruded tubing.

[0035] It will be apparent from the foregoing that, while particularforms of the invention have been illustrated and described, variousmodifications can be made without departing from the spirit and scope ofthe invention. For example, while the balloon is discussed primarily interms of a blend of polyether block amides, it should be understood thatother blends which have the desired characteristics outlined above mayalso be used. Although individual features of embodiments of theinvention may be described or shown in some of the drawings and not inothers, those skilled in the art will recognize that individual featuresof one embodiment of the invention can be combined with any or all thefeatures of another embodiment. Other modifications may be made withoutdeparting from the scope of the invention.

What is claimed is:
 1. A balloon for intracorporeal use formed of afirst blend of a first polymeric material having a first Shore durometerhardness, and a second polymeric material having a second Shoredurometer hardness less than the first Shore durometer hardness.
 2. Theballoon of claim 1 wherein the blend comprises about 10% to about 90% ofthe first polymeric material and about 90% to about 10% of the secondpolymeric material.
 3. The balloon of claim 1 wherein an amount of thefirst polymeric material in the blend is not greater than ane amount ofthe second polymeric material.
 4. The balloon of claim 1 wherein thehoop strength is about 22,000 psi to about 32,000 psi.
 5. The balloon ofclaim 1 wherein the axial growth from a nominal pressure to a ratedburst pressure of the balloon is less than about 10% of a working lengthof the balloon.
 6. The balloon of claim 5 wherein the nominal pressureof the balloon is about 6 to about 10 atm and the rated burst pressureis at least about 14 to about 16 atm.
 7. A balloon catheter, comprisinga) a shaft having a proximal end, a distal end, and a lumen extendingtherein; and b) a balloon on the shaft formed of a blend of polymericmaterials comprising a first polyether block amide polymeric materialhaving a first Shore durometer hardness, and a second polyether blockamide polymeric material having a second Shore durometer hardness lessthan the first Shore durometer hardness.
 8. The balloon catheter ofclaim 7 wherein the balloon has a compliance which is not substantiallygreater than a compliance of a balloon consisting of the first polyetherblock amide polymeric material.
 9. The balloon catheter of claim 7wherein the balloon has a compliance which is not greater than acompliance of a balloon consisting of the first polyether block amidepolymeric material.
 10. The balloon catheter of claim 7 wherein theblend has a flexural modulus lower than a flexural modulus of the firstpolyether block amide polymeric material.
 11. The balloon catheter ofclaim 7 wherein the balloon has a mean rupture pressure notsubstantially lower than a balloon consisting of the first polyetherblock amide polymeric material.
 12. The balloon catheter of claim 7wherein the blend comprises an amount of the second polyether blockamide polymeric material which is not less than an amount of the firstpolyether block amide polymeric material.
 13. The balloon catheter ofclaim 7 wherein the second polyether block amide polymeric materialcomprises about 20% to about 80% by weight of the total blend.
 14. Theballoon catheter of claim 7 wherein the second polyether block amidepolymeric material comprises about 40% to about 60% by weight of thetotal blend.
 15. The balloon catheter of claim 7 wherein the firstpolyether block amide polymeric material comprises about 20% to about80% by weight of the total blend.
 16. The balloon catheter of claim 7wherein the first polyether block amide polymeric material comprisesabout 40% to about 50% by weight of the total blend.
 17. The ballooncatheter of claim 7 wherein the first polyether block amide polymericmaterial has a Shore durometer hardness of about 60D to about 72D. 18.The balloon catheter of claim 7 wherein the first polyether block amidepolymeric material has a Shore durometer hardness of about 70D.
 19. Theballoon catheter of claim 7 wherein the second polyether block amidepolymeric material has a Shore durometer hardness of about 55D to about70D.
 20. The balloon catheter of claim 7 wherein the second polyetherblock amide polymeric material has a Shore durometer hardness of about63D.
 21. The balloon catheter of claim 7 wherein the balloon has acompliance of not greater than about 0.045 mm/atm from a nominal to arated burst pressure of the balloon.
 22. The balloon catheter of claim 7wherein the balloon has a compliance of not greater than about 0.045mm/atm over a pressure range of about 8 atm to about 14 atm.
 23. Theballoon catheter of claim 7 wherein the balloon has a compliance ofabout 0.03 mm/atm to about 0.035 mm/atm from a nominal to a rated burstpressure of the balloon.
 24. The balloon catheter of claim 7 wherein theballoon has a flexural modulus which is less than a flexural modulus ofa balloon consisting of the first polyether block amide polymericmaterial.
 25. The balloon catheter of claim 4 wherein the balloon has aflexural modulus of about 10 to about 14 gram/mm.
 26. The ballooncatheter of claim 7 wherein the balloon has a dual wall thickness ofabout 0.025 to about 0.056 mm, and a nominal outer diameter of about 1.5to about 5.0 mm.
 27. A balloon catheter, comprising a) an elongatedshaft having a proximal end, a distal end, and at least one lumentherein; and b) a balloon formed at least in part of a blend of a firstpolyether block amide polymeric material having a first Shore durometerhardness of about 70D to about 72D, and being about 30% to about 70% byweight of the total blend; and a second polyether block amide polymericmaterial having a second Shore durometer hardness less than the Shoredurometer hardness first polyether block amide polymeric material, beingabout 40% to about 75% by weight of the total blend.
 28. The ballooncatheter of claim 27 wherein the second polyether block amide polymericmaterial has a Shore durometer hardness of about 55D to about 63D. 29.The balloon catheter of claim 28 wherein the balloon has a compliance ofabout 0.025 to about 0.040 mm/atm from a nominal to a rated burstpressure.
 30. The balloon catheter of claim 27 wherein the secondpolyether block amide polymeric material is about 60% by weight of thetotal blend and the first polyether block amide polymeric material isabout 40% by weight of the total blend.